The Eiffel Tower is seen at night in front of the Sacre Coeur Basilica on Montmartre (L) in Paris, France, December 7, 2015. The French capital hosts the World Climate Change Conference 2015 (COP21) from November 30 to December 11.

LE BOURGET, FRANCE — Soon, this sprawling city-like complex will be gone. The negotiating rooms will be emptied, the media bullpens will fall silent, and the temporary structures will be dismantled. Once again, the site of the 2015 UN climate summit will revert to being an airfield in a suburb northeast of Paris.

The hope is that what remains is an enhanced global ambition to curb climate change and safeguard against its effects.

There is no shortage of issues that continue to divide negotiators here. But one area in which there is growing convergence is in the unique legal nature of the expected agreement.

Paris is different. Parts of the agreement will indeed be legally binding, officials and observers say – such as how to monitor progress and to ensure transparent data collection. But the soul of the agreement – the 158 voluntary pledges on climate action submitted to the UN – is likely to fall outside the bounds of traditional legal force.

Even before the delegates met, critics charged that this hands-off treatment would make any deal toothless, since the core commitments will be voluntary "contributions."

But there's a sense here in Le Bourget that the decentralized, non-binding approach is exactly what has brought so much weight and value to this year's summit. Officials aim to bring more parties to the table, even if it's at the expense of legal enforcement. Rather than be bound to a paper text, countries are instead bound to one another.

"In effect, what you're creating is a system of institutionalized peer pressure," Elliot Diringer, executive vice president of the Washington-based Center for Climate and Energy Solutions tells the Christian Science Monitor on the sidelines of the Paris talks. "We see it working already. The mere expectation that countries offer up contributions has led to this tremendous surge without a single word of the agreement being agreed.”

Scope of participation

To be sure, some of the legal limbo is a function of political expediency: Domestic politics in the US and elsewhere make binding climate commitments a nonstarter. That means putting key parts of the dealoutside the bounds of the US definition of the word "treaty."

What began as realpolitik, however, has proven itself to be shrewd strategy. Whereas a stringent, top-down system might attract only the most willing and capable, COP21's flexible approach has enabled nearly every party to put on the table what it can, without the fear of punishment should circumstances change. That means everyone from China – representing a third of global emissions – all the way across to The Gambia – representing 0.02 percent of global emissions – has laid out how they will slash greenhouse-gas emissions.

Even Russian President Vladimir Putin, who has long scoffed at the international climate process, told surprised delegates last Monday that "climate change has become one of the gravest challenges that humanity is facing."

What's more, international agreements are, to some degree, always voluntary, notes Robert Stavins, director of the environmental economics program at Harvard University.

"The United Nations does not have a police force," Professor Stavins says. "We don't withhold highway funds from Russia, the United States or Kazakhstan because they don't do something. So you can always drop out."

Virtuous cycles

Indeed, that’s what happened with the Kyoto Protocol. After the US opted not to ratify the protocol, a series of major economies including Russia, Canada, and Japan dropped out. Today, the protocol covers only Europe and New Zealand, about 14 percent of global emissions, according to Professor Stavins. Meanwhile, pledges made in advance of the Paris agreement cover countries representing 98 percent of global emissions, according to data compiled by World Resources Institute, a think tank based in Washington.

Of course, this only counts if countries act.It also assumes that the combined action is enough to stave off the worst impacts of climate change.

This, again, is where observers hope scope of participation – as opposed to degree of enforcement – can play a role. The sheer number of parties involved provides an economies of scale that can create a feedback loop over time.

"The result is a cycle of mutual reinforcement: Decreasing costs enable larger emissions reductions, and larger emissions reductions drive further cuts to cost," writes Jessika Trancik, a professor at the Massachusetts Institute of Technology and lead author of a recent study that looks into these kinds of virtuous cycles.

Accountability

For some, this still leaves too much to chance. The poorest and most vulnerable countries – who already suffer from increased drought and rising seas – want hard, legally binding commitments, calling it a matter of principle and trust: In an interview with the Monitor last week, Giza Gaspar Martins, chair of the bloc of Least Developed Countries, emphasized that legally binding commitments contribute to an overall sense of trust among nations.

It's also a matter of clarity. If there's one thing that irks developing countries the most in these talks, it's the tendency of developed countries to blur the details with legalese.

For example, there is a debate over who should contribute financing for clean-energy and climate adaptation projects across the globe. Is it only the responsibility of the developed world? Or, as some have suggested, "countries in a position to do so"?

When asked about this specific phrase at a press conference last week, Nozipho Mxakato-Diseko, a South African diplomat who leads a major group of developing countries, was openly flummoxed by this classic example of bureaucratic hedging.

"How do you put in a legally binding instrument 'countries in a position to do so'?" she said. "In my family, with the children, I tell them ... 'You, John, will clean the room. You, Grace, will do the dishes.' There is no 'someone in a position to do so will wipe the floor.'"

"I need accountability," she added. "I really do need accountability. And I need to know, above all, that the floor has been cleaned."